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What is the difference of putting a push button switch between a switching power supply and a PWM speed controller (dial on 100%) or it between PWM controller and a 12V DC motor (to turn it on and off repeteadly)?

If the motor has huge initial current, will be any harm for the motor, power supply or speed controller by numerous on and offs operated with the switch?

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    \$\begingroup\$ This is too vague for a meaningful answer, only for guesses, as I'm sure a regular like yourself knows. Please edit you question and detail the situation, with a schematic (not a giant photo of a sketch). The better the quality of your question, the better the quality of the answers you will attract. \$\endgroup\$ – TonyM Nov 17 '20 at 9:05
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The best way to turn a motor with a speed controller on and off repeatedly is to use the controller to do that. A good controller should have an electronic start/start input. If the controller doesn't have that, see if you can command zero speed. It is not the best practice to repeatedly disconnect either the power input to the controller or the power output to the motor. If you need to disconnect power, doing it at the controller input is probably preferable. The design details might indicate otherwise.

Industrial motor speed controllers (drives) typically have a potentiometer, keypad or signal input speed command that can remain undisturbed during all operation including power down. When the drive receives a start command the motor is accelerated with a preset ramp time with a current limited override. That allows the motor to accelerate to the set speed as quickly as possible without over stressing anything. Stopping is similar.

The drive is typically powered down only at the end of the day or when the operator takes a break, rarely more frequently than that. Emergency stop may be implemented with a contactor and a spring-set friction brake.

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  • \$\begingroup\$ if you are familiar with dental micromotors, they come with two type of foot pedals, variable speed (like throttle) and non variable, the variable use poetentiometer I think with a pwm speed controller circuit, the other is like a simple switch; the thing is when the rpm is set on 60% on control box for example, when it is on hand mode it works constantly, but on foot mode it turns on each time we push the pedal, so if the motor has huge initial current how it is possible to run the motor from zero to wanted rpm in no time like a micromotor without any damage over and over again? \$\endgroup\$ – UnoBianconero Nov 18 '20 at 6:10

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